For four of the last five years I've bee the staff shooter for an event put on my a slot car modeling club here in Japan (I couldn't make it the other year). They invite a lot of (mostly) retired drivers of F-1 and other types to come compete in a closed event, using painstakingly detailed handmade models of the cars the drivers used to race. Every year there are reporters and photographers there from several magazines and this year we also had a television crew from the Japanese equivalent of ESPN.
Point is....there was some very serious high-dollar gear (CaNikon) there to cover the event. The event is club members, invited drivers, members of the press....and yours truly. This year yours truly shot the entire thing with the Fujifilm X10. I took my K-5 along, but it ended up sitting on a windowsill next to my camera bag for the entire event; I never even went near it.
I ended up with about 550 shots, getting probably about 400 shots on one battery through diligently turning the camera off when not in active use, using AF.S. for most of the day (with rear screen turned off), and doing only the minimal amount of chimping I thought I could get by with. I could have gotten more had I not used AF.C. and had I not experimented with using the flash a bit. There was enough light from windows, skylights, and interior ceiling lights that I felt confident in just putting the X10 in auto ISO (max 3200) and just letting it do its thing, as it has demonstrated before that it is quite capable of minimal and controllable noise up to 3200 with no problem. For much of the event I shot in S mode with the shutter at 1/250 or thereabouts. Later in the afternoon I noticed I had lost a stop or two of light from the windows and skylights so I dropped down to 1/125 and was just a wee bit more careful of my subjects to avoid blur. It was about that time that I started messing with the flash as well.